Semiconductor materials
Elements that are used as A material that will only allow charge to move easily through it under some conditions, for example when 'doped' with impurities., such as silicon and germanium, have four outer shell Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons.. This means that they can form four bonds with other identical atoms.
In a crystal of pure silicon each silicon atom is surrounded by four other silicon atoms. In this state the silicon will not conduct.
Pure silicon can be doped with tiny quantities of impurities by diffusing the impurities as a gas into the liquid semiconductor before it crystallizes.